1. Technical Field
This invention relates to portable frequency modulation transmission systems and, more particularly, to providing dual modes of use in such systems.
2. Description of the Prior Art
Cordless telephone station systems employing infrared transmission are known comprising a portable cordless transmitter with remote microphone and supervisory signaling capabilities. One such transmitter is described in Anglikowski et al., U.S. Pat. No. 4,221,932. The supervisory signaling is achieved by shifting the carrier frequency of the transmitted signal for indicating a low battery condition and transmitter turnoff. There is no keyboard data input capability.
Alternatively, portable cordless transmitters are known for transmitting keyboard entered data signals for controlling a cathode ray tube television terminal. For example, Richter et al., U.S. Pat. No. 4,091,272, discloses an infrared remote controlled command system for operating a television receiver. Keys of a keyboard are provided for selecting the television channel or for controlling the volume level.
With the onset of viewdata services wherein a combination telephone and television terminal may be provided to telephone subscribers, it is believed desirable that both voice and data be enterable from the remote portable transmitter. The user of the transmitter would not have to be located in close proximity to the viewdata terminal and would be able to remotely control its television and telephone functions.